EVALUASI KETELITIAN GEOMETRIK PETA ORTOFOTO (Studi Kasus : Sebagian Proyek Pemetaan Gunung Merapi Yogyakarta)

Measurements using Airborne Laser Scanning (ALS) is one way to produce geospatial data quickly. This method has advantages in terms of rapid data acquisition time and high accuracy measurement results. However, ALS only produces point cloud data not image of the object. Combination of aerial photo exposed using medium format camera and point cloud data can provide orthophoto map. Orthophoto map�s quality can be determined using quality control by accuracy test. This accuracy test consists of two objects, namely radiometric accuracy test and geometric accuracy test. This research aims to evaluate the geometric accuracy, on the slope area and flat area. Materials used in this research is four tiles orthophoto and three tiles contour. The tiles covered Purwobinangun area and Universitas Gadjah Mada area . This data was obtained from the Department of Geodetic Engineering UGM. Overall study area are 7,60932 km2. The research begins by determining the test line on the orthophoto for 80 points. The identified test lines were then measured directly on the field and on the orthophoto map. Distances and height differences observed on the orthophoto map were compared to those observed on the field. To avoid blunder data, statistical test was implemented. RMSE then was computed and compared to the NSSDA standard accuracy. The result shows that the distance accuracy for the flat area and slope area are 17,69 cm and 21,79 cm, while the height differences accuracy for the flat area and slope area are 14,98 cm and 16,32 cm. According to NSSDA standard accuracy, these accuracy can produce contour interval two feet (60 cm). It means that the appropriate scale of orthophoto map is 1 :1200. Scale 1 : 1200 is generated on the basis of dimensional accuracy not positional accuracy. Orthophoto maps with a scale of 1: 1200 were used in this study can be used for spatial planning and base map for land registration. It can also be used for boundary making for the village

ORTOREKTIFIKASI CITRA QUICKBIRD MENGGUNAKAN MODEL ELEVASI DIGITAL DENGAN BERBAGAI KETELITIAN DAN BERBAGAI JUMLAH TITIK KONTROL TANAH

The rapid development in an area, required more geospatial information. One alternative for obtaining geospatial information with high precision, wide area coverage and rapid data collection is by using orthorectified image and rectified image. To make orthorectified image, it needs Digital Elevation Model (DEM) data and ground control points (GCPs), while to make rectified image need GCPs. However, how various DEM and the number of GCP affect the quality of orthorectified image currently is not exactly defined. How various the number of GCP affect the quality of rectified image also currently is not exactly defined. This study aimed to evaluate the effects of various DEM quality and various number of GCP to the result of orthorectified image and also the effects of various number of GCP to the result of rectified image. This research employed the following data: two satellite imageries with spatial resolution 60 cm on Kaliurang area with slope more than 20% and on UGM with slope less than 2%, four DEM namely LiDAR DEM with accuracy 30 cm, XSAR DEM with accuracy 5 m, SRTM 90m DEM with accuracy 16 m, and ASTER GDEM with accuracy 17 m, and also orthophoto with map scale 1 : 1000. The width of the study area is 4 km 2 . The research started with determining of GCP and check points (CP) on the orthophoto map and satellite imagery as much as 20 GCPs and 20 CPs on the Kaliurang area as well as 20 GCPs and 20 CPs on UGM area. Orthorectification with Rational Polynomial Coefficients (RPC) method was performed by using various DEM quality and various number of GCP, while rectification with second order polynomial method was performed by using various number of GCP. The coordinate of check points were identified on the orthorectified image, on the rectified image, and on the orthophoto map in the Kaliurang area and in the UGM area. Check points coordinate observed on the orthophoto map were compared to those observed on the orthorectified image and on the rectified image. Statistical test was implemented on the check point orthorectified image and on the rectified image in the Kaliurang area and in the UGM area. Root Mean Square Error (RMSE) then was computed and compared to the BIG accuracy standard. The result shows that the number of GCP have more effect to the accuracy of orthorectified image than the quality of DEM. The orthorectified image have an accuracy of less than 1.5 m, while the rectified image have an accuracy of more than 1,5 m. According to BIG accuracy standard, orthorectified image and rectified image can be used to make a map of scale at 1 : 2500 and 1 : 5000. Base on the scale, orthorectified image and rectified image from this research can be used for spatial planning, base map for land registration, and for village boundary making for the village

Perbandingan Ketelitian Geometrik Citra Satelit Resolusi Tinggi dan Foto Udara untuk Keperluan Pemetaan Rupabumi Skala Besar = Geometric Accuracy Comparison between High Resolution Satellite Imagery and Aerial Photo for Large Scale Topographic Mapping

Selain foto udara, citra satelit resolusi tinggi (CSRT) saat ini merupakan data dasar yang digunakan untuk pemetaan Rupabumi Indonesia (RBI) skala 1:5.000. Meski digunakan untuk menghasilkan peta pada level skala yang sama, namun foto udara dan CSRT memiliki perbedaan spesifikasi terkait kualitas geometriknya. Penelitian ini bertujuan untuk mendapatkan gambaran mengenai kemampuan data CSRT dan foto udara, sehingga bisa menjadi salah satu landasan dalam membuat kebijakan terkait. Aspek yang dikaji adalah ketelitian geometrik CSRT dan foto udara dari sisi resolusi dan akurasi posisi. Data CSRT yang digunakan adalah citra hasil orthorektifikasi, yaitu wilayah Bolaang Mongondow Timur, Ambon, Sumba Timur, Morowali, Kualatanjung, dan Gorontalo, sedangkan data foto udara yang digunakan adalah wilayah Palu dan Bogor. Sebagai perbandingan hasil digunakan acuan standar di negara lain seperti American Society for Photogrammetry and Remote Sensing (ASPRS) dan National Technical Document For Establishing Cartographic Base in India. Hasil penelitian menunjukkan ketelitian geometri CSRT berada pada skala 1:5.000 kelas 2 dan 3, sedangkan ketelitian foto udara berada pada skala 1:5.000 kelas 1. Secara resolusi, foto udara 2-4 kali lebih detail dari CSRT. Meski demikian, CSRT memiliki keunggulan yaitu cakupan footprint yang jauh lebih luas daripada foto udara, sehingga dalam keperluan praktis CSRT lebih sering digunakan untuk menghasilkan data RBI skala besar dibandingkan foto udaraHlm. 125-13